U.S. patent application number 13/460494 was filed with the patent office on 2012-09-20 for spunlaid fibers comprising coated calcium carbonate, processes for their production, and nonwoven products.
Invention is credited to Larry H. McAmish, David A. Skelhorn.
Application Number | 20120238175 13/460494 |
Document ID | / |
Family ID | 42337334 |
Filed Date | 2012-09-20 |
United States Patent
Application |
20120238175 |
Kind Code |
A1 |
McAmish; Larry H. ; et
al. |
September 20, 2012 |
SPUNLAID FIBERS COMPRISING COATED CALCIUM CARBONATE, PROCESSES FOR
THEIR PRODUCTION, AND NONWOVEN PRODUCTS
Abstract
Disclosed herein are spunlaid fibers comprising at least one
polymeric resin and at least one filler having an average particle
size of less than or equal to about 5 microns and/or having a top
cut of less than about 15 microns, wherein the at least one filler
is present in an amount of less than about 40% by weight, relative
to the total weight of the spunlaid fibers. Also disclosed herein
is a method for producing spunlaid fibers comprising adding calcium
carbonate to at least one polymeric resin and extruding the
resulting mixture. Further disclosed herein are nonwoven fabrics
comprising such spunlaid fibers and methods for producing them.
Inventors: |
McAmish; Larry H.;
(Marietta, GA) ; Skelhorn; David A.; (Cumming,
GA) |
Family ID: |
42337334 |
Appl. No.: |
13/460494 |
Filed: |
April 30, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12520103 |
Aug 14, 2009 |
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PCT/US08/53964 |
Feb 14, 2008 |
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13460494 |
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60941684 |
Jun 3, 2007 |
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60969100 |
Aug 30, 2007 |
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60870861 |
Dec 20, 2006 |
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Current U.S.
Class: |
442/417 ;
428/394 |
Current CPC
Class: |
D04H 1/728 20130101;
Y10T 428/2967 20150115; Y10T 442/699 20150401; D04H 3/153
20130101 |
Class at
Publication: |
442/417 ;
428/394 |
International
Class: |
D02G 3/04 20060101
D02G003/04; D04H 3/005 20120101 D04H003/005 |
Claims
1. A spunlaid fiber comprising at least one polymeric resin and at
least one coated filler having an average particle size of less
than or equal to about 3 microns, wherein the at least one coated
filler is coated calcium carbonate and is present in the fiber in
an amount less than about 40 wt %, relative to the total weight of
the spunlaid fiber.
2. The spunlaid fiber of claim 1, wherein the calcium carbonate is
present in an amount less than about 25 wt %, relative to the total
weight of the spunlaid fiber.
3. (canceled)
4. (canceled)
5. The spunlaid fiber of claim 1, wherein the coating of the
calcium carbonate is at least one organic material chosen from
fatty acids and salts and esters thereof.
6. The spunlaid fiber of claim 5, wherein the at least one organic
material is chosen from stearic acid, stearate, ammonium stearate,
and calcium stearate.
7-12. (canceled)
13. The spunlaid fiber of claim 1, wherein the calcium carbonate
has an average particle size of less than or equal to about 2
microns.
14-16. (canceled)
17. The spunlaid fiber of claim 1, wherein the calcium carbonate
has an average particle size of less than or equal to about 100% of
the average diameter of the spunlaid fibers.
18. The spunlaid fiber of claim 1, wherein the calcium carbonate
has an average particle size ranging from about 1 micron to about 3
microns.
19-23. (canceled)
24. A nonwoven fabric comprising at least one spunlaid fiber of
claim 1.
25. The spunlaid fiber of claim 1, wherein the calcium carbonate
has a top cut of about 15 microns or less.
26. The spunlaid fiber of claim 25, wherein the calcium carbonate
has a top cut of about 10 microns.
27. (canceled)
28. The spunlaid fiber of claim 25, wherein the calcium carbonate
has a top cut ranging from about 4 microns to about 15 microns.
29. (canceled)
30. (canceled)
31. The spunlaid fiber of claim 25, wherein the calcium carbonate
has a top cut of not more than about 100% of the average diameter
of the spunlaid fiber.
32. (canceled)
33. (canceled)
34. A spunlaid fiber comprising at least one polymeric resin and
coated calcium carbonate having a top cut of about 15 microns or
less, wherein the coated calcium carbonate is present in the fiber
in an amount less than about 40 wt %, relative to the total weight
of the spunlaid fiber.
35-37. (canceled)
38. The spunlaid fiber of claim 34, wherein the coating of the
coated calcium carbonate is at least one organic material chosen
from fatty acids and salts and esters thereof.
39-45. (canceled)
46. The spunlaid fiber of claim 34, wherein the calcium carbonate
has a top cut of about 12 microns.
47-49. (canceled)
50. The spunlaid fiber of claim 34, wherein the calcium carbonate
has a top cut ranging from about 4 microns to about 15 microns.
51-54. (canceled)
55. The spunlaid fiber of claim 34, wherein the calcium carbonate
has a top cut of not more than about 100% of the average diameter
of the spunlaid fiber.
56. The spunlaid fiber of claim 34, wherein the calcium carbonate
has an average particle size of less than or equal to about 5
microns.
57-114. (canceled)
115. A thermoformed spunlaid fiber comprising at least one
polymeric resin and at least one coated filler having an average
particle size of less than or equal to about 3 microns and having a
top cut of about 15 microns or less, wherein the at least one
coated filler is present in the fiber in an amount less than about
40 wt %, relative to the total weight of the thermoformed spunlaid
fiber.
116-118. (canceled)
119. The thermoformed spunlaid fiber of claim 115, wherein the at
least one coated filler comprises a coating, and the coating is at
least one organic material chosen from fatty acids and salts and
esters thereof.
Description
RIGHT OF PRIORITY AND INCORPORATION BY REFERENCE
[0001] This application hereby claims the right of priority to and
incorporates by reference in their entireties U.S. Provisional
Patent Application No. 60/870,861 filed Dec. 20, 2006, U.S.
Provisional Patent Application No. 60/941,684 filed Jun. 3, 2007,
U.S. Provisional Patent Application No. 60,969,100 filed Aug. 30,
2007, and International PCT Application No. PCT/US2007/087919 filed
Dec. 18, 2007.
FIELD OF THE INVENTION
[0002] Disclosed herein are spunlaid fibers comprising less than
about 40 wt % of coated calcium carbonate, relative to the total
weight of the fibers. Also disclosed herein is a method for
producing spunlaid fibers comprising adding coated calcium
carbonate to at least one polymeric resin and extruding the
resulting mixture to then form the fibers. Further disclosed herein
are nonwoven fabrics and products comprising such spunlaid fibers
and methods for producing them.
BACKGROUND OF THE INVENTION
[0003] Many nonwoven commercial products are formed from spunlaid
fibers of polymeric resins. For instance, spunlaid fibers may be
used to make diapers, feminine hygiene products, adult incontinence
products, packaging materials, wipes, towels, dust mops, industrial
garments, medical drapes, medical gowns, foot covers, sterilization
wraps, table cloths, paint brushes, napkins, trash bags, various
personal care articles, ground cover, and filtration media.
[0004] Spunlaid fibers are generally made by a continuous process,
in which the fibers are spun and dispersed in a nonwoven web. Two
examples of spunlaid processes are spunbonding or meltblowing. In
particular, spunbonded fibers may be produced by spinning a
polymeric resin into the shape of a fiber, for example, by heating
the resin at least to its softening temperature, extruding the
resin through a spinerette to form fibers, and transferring the
fibers to a fiber draw unit to be collected in the form of spunlaid
webs. Meltblown fibers may be produced by extruding the resin and
attenuating the streams of resin by hot air to form fibers with a
fine diameter and collecting the fibers to form spunlaid webs.
[0005] The textile industry consumes a large amount of
thermoplastic polymeric resin each year for the production of
nonwoven products. While it is known to incorporate various mineral
fillers such as calcium carbonate and kaolin during production of
nonwoven products and plastic products such as films and molded
parts, it is not general practice to include large amounts of such
fillers in polymeric nonwoven fibers. Previously, the cost of
virgin resin was lower than the cost of concentrates composed of
resins and mineral fillers and, thus, there was not a recognized
need to incorporate significant amounts of such fillers into
nonwoven products. However, due to recent increases in resin
prices, there is now a cost benefit associated with increasing the
quantity of mineral fillers and decreasing the quantity of resin in
nonwoven products. By incorporating an optimum amount of at least
one mineral filler, such as coated calcium carbonate, it is
possible to reduce the required amount of virgin resin material
while still producing a nonwoven product having comparable quality
in terms of fiber strength, texture, and/or appearance.
[0006] The prior art appears to disclose nonwoven products
comprising various amounts of inorganic compounds and/or mineral
fillers. For example, U.S. Pat. No. 6,797,377 appears to disclose
nonwoven webs comprising from 0.1 to 10 wt % of at least one
mineral filler such as calcium carbonate, but imposes the
limitation of the filler being used in conjunction with titanium
dioxide in a mixture of at least two resin polymers. U.S. Pat. No.
6,759,357 likewise appears to disclose nonwoven fabrics comprising
from 0.0015 to 0.09 wt % of at least one inorganic compound. S.
Nago and Y. Mizutani, "Microporous Polypropylene Fibers Containing
CaCO3 Filler," 62 J. Appl. Polymer Sci. 81-86 (1996), also appears
to discuss polypropylene-based nonwoven fibers comprising 25 wt %
calcium carbonate. WO 97/30199 may disclose fibers consisting
essentially of 0.01 to 20 wt % inorganic particles, substantially
all having a Mohs hardness of less than about 5 and at least 90 wt
% of the inorganic particles having a particle size of less than 10
microns. However, those references do not appear to disclose
reducing the impact of the filler on the properties of the nonwoven
fibers at least through changes to the particle size of the coated
calcium carbonate by its average particle size and/or by its top
cut.
[0007] Thus, it would be useful to provide spunlaid fibers that
incorporate higher levels of coated calcium carbonate, thereby
allowing for more cost-effective nonwoven products that have
comparable quality in terms of strength, texture, and/or
appearance.
BRIEF DESCRIPTION OF THE FIGURES
[0008] FIG. 1 is an SEM photograph of fibers made with 20% coated
calcium carbonate having a top cut of about 20 showing fiber
breakage.
[0009] FIG. 2 is a photograph of a fiber web containing a "fiber
clump" or "fiber bundle" caused by processing problems.
[0010] FIG. 3 is a graphical illustration showing a typical
particle size distribution of a calcium carbonate product
(FiberLink.TM. 101S manufactured in the United States by Imerys,
Inc.) as disclosed herein.
[0011] FIG. 4 is an SEM photograph of fibers made with 5% uncoated
calcium carbonate showing uncoated calcium carbonate particles
located on the outside of the fibers.
[0012] FIG. 5 is a chart comparing the fibers diameters produced in
accordance with the present invention as examples using different
loadings of filler.
[0013] FIG. 6 is an SEM photograph of fibers made without any
filler.
[0014] FIG. 7 is an SEM photograph of fibers made with 25% coated
calcium carbonate in accordance with the present invention.
[0015] FIG. 8 is a SEM photograph of a fiber web embossed with
diamond shapes.
[0016] FIG. 9 is a graphical illustration of the results of a drop
dart test conducted on a nonwoven fabric produced according to
Examples 1-6 of the present disclosure.
[0017] FIG. 10 is a graphical illustration providing the maximum
load (machine direction) results of a tensile strength test
conducted on a nonwoven fabric produced according to Examples 1-6
of the present disclosure.
[0018] FIG. 11 is a graphical illustration providing the maximum
load (transverse direction) results of a tensile strength test
conducted on a nonwoven fabric produced according to Examples 1-6
of the present disclosure.
[0019] FIG. 12 is a graph providing the maximum percent strain
(machine direction) results of a tensile strength test conducted on
a nonwoven fabric produced according to Examples 1-6 of the present
disclosure.
[0020] FIG. 13 is a graphical illustration providing the maximum
percent strain (transverse direction) results of a tensile strength
test conducted on a nonwoven fabric produced in accordance Examples
1-6 of the present disclosure.
[0021] FIG. 14 is a chart comparing the diameters of fibers
produced as described in Examples 7-11 using different loadings of
filler.
[0022] FIG. 15 is a chart comparing the basis weight of the fabrics
produced according to Examples 7-11.
[0023] FIG. 16 is a graphical illustration of the results of a drop
dart test conducted on a nonwoven fabric produced according to
Examples 7-11 of the present disclosure.
[0024] FIG. 17 is a graphical illustration providing the maximum
load (machine direction) results of a tensile strength test
conducted on a nonwoven fabric produced according to Examples 7-11
of the present disclosure.
[0025] FIG. 18 is a graphical illustration providing the maximum
load (cross direction) results of a tensile strength test conducted
on a nonwoven fabric produced according to Examples 7-11 of the
present disclosure.
[0026] FIG. 19 is a graph providing the maximum percent strain
(machine direction) results of a tensile strength test conducted on
a nonwoven fabric produced according to Examples 7-11 of the
present disclosure.
[0027] FIG. 20 is a graphical illustration providing the maximum
percent strain (cross direction) results of a tensile strength test
conducted on a nonwoven fabric produced according to Examples 7-11
of the present disclosure.
[0028] FIG. 21 is a graphical illustration showing the difference
in potential after electrostatic charging webs not containing
coated calcium carbonate and webs containing 5% and 20% coated
calcium carbonate.
SUMMARY OF THE INVENTION
[0029] Disclosed herein are spunlaid fibers comprising at least one
polymeric resin and coated calcium carbonate having an average
particle size less than or equal to about 5 microns, wherein the
calcium carbonate is present in an amount of less than about 40% by
weight, relative to the total weight of the fibers.
[0030] In addition, disclosed herein are spunlaid fibers comprising
at least one polymeric resin and coated calcium carbonate having a
top cut of about 15 microns or less, wherein the coated calcium
carbonate is present in an amount of less than about 40% by weight,
relative to the total weight of the fibers.
[0031] Also disclosed herein is a method for producing spunlaid
fibers comprising adding coated calcium carbonate to at least one
polymeric resin and extruding the resulting mixture, wherein the
coated calcium carbonate has an average particle size less than or
equal to about 5 microns, and wherein the coated calcium carbonate
is present in the final product in an amount of less than about 40%
by weight. Further disclosed herein is a method for producing
spunlaid fibers comprising at least one polymeric resin and coated
calcium carbonate having a top cut of about 15 microns or less,
wherein the coated calcium carbonate is present in an amount of
less than about 40% by weight, relative to the total weight of the
fibers.
[0032] Further disclosed herein are nonwoven fabrics and products
comprising such spunlaid fibers, and methods for producing those
fabrics and products.
DETAILED DESCRIPTION OF THE INVENTION
Nonwoven Fibers
[0033] At Least One Polymeric Resin
[0034] Disclosed herein are spunlaid fibers and products comprising
increased amounts of coated calcium carbonate filler. The spunlaid
fibers disclosed herein comprise at least one polymeric resin. In
one embodiment, the at least one polymeric resin is chosen from
conventional polymeric resins that provide the properties desired
for any particular nonwoven product or application. In another
embodiment, the at least one polymeric resin is chosen from
thermoplastic polymers, including but not limited to: polyolefins,
such as polypropylene and polyethylene homopolymers and copolymers,
including copolymers with 1-butene, 4-methyl-1-pentene, and
1-hexane; polyamides, such as nylon; polyesters; copolymers of any
of the above-mentioned polymers; and blends thereof.
[0035] Examples of commercial products suitable as the at least one
polymeric resin include, but are not limited to: Exxon 3155, a
polypropylene homopolymer having a melt flow rate of about 30 g/10
min, available from Exxon Mobil Corporation; PF 305, a
polypropylene homopolymer having a melt flow rate of about 38 g/10
min, available from Montell USA; ESD47, a polypropylene homopolymer
having a melt flow rate of about 38 g/10 min, available from Union
Carbide; and 6D43, a polypropylene-polyethylene copolymer having a
melt flow rate of about 35 g/10 min, available from Union
Carbide.
[0036] The at least one polymeric resin may be incorporated into
the fibers of the present disclosure in an amount of greater than
or equal to about 60 wt % relative to the total weight of the
fibers. In one embodiment, the at least one polymer resin is
present in the fibers in an amount ranging from about 60 to about
90 wt %. In another embodiment, the at least one polymer is present
in the fibers in an amount ranging from about 75 to about 90 wt %.
In a further embodiment, the at least one polymer is present in the
fibers in an amount ranging from about 80 to about 90 wt %. In yet
another embodiment, the at least one polymer is present in the
fibers in an amount of greater than or equal to about 75 wt %.
[0037] Coated Calcium Carbonate
[0038] The nonwoven fibers in accordance with the present
disclosure also comprise at least one filler. In one embodiment,
the at least one filler is coated calcium carbonate, a filler
commonly used in the formation of various polymeric products. In
another embodiment, the at least one filler is chosen from the
group consisting of coated calcium carbonate, talc, and clay.
[0039] Coated calcium carbonate products suitable for use in the
fibers of the present disclosure include, but are not limited to,
those commercially available. In a preferred embodiment, the coated
calcium carbonate is chosen from those products sold under the
names FiberLink.TM. 101S and 103S by Imerys, Inc. In another
embodiment, the coated calcium carbonate is the product sold under
the name MAGNUM GLOSS.RTM. by the Mississippi Lime Company. In a
further embodiment, the coated calcium carbonate is the product
sold under the name ALBAGLOS.RTM. by Specialty Minerals, Inc. In
yet another embodiment, the coated calcium carbonate is the product
sold under the name OMYACARB.RTM. by OMYA, Inc. In yet a further
embodiment, the coated calcium carbonate is the product sold under
the name HUBERCARB.RTM. by Huber, Inc. In a less preferred
embodiment, the coated calcium carbonate is the product sold under
the name Supercoar by Imerys, Inc. The commercially available
coated calcium carbonate products may be available in the form of
dry powders having defined particle size ranges; however, not all
commercial coated calcium carbonate products will exhibit a
particle size and distribution appropriate for use in accordance
with the present disclosure.
[0040] The particle size of the at least one filler may affect the
maximum amount of filler that can be effectively incorporated into
the nonwoven fibers disclosed herein, as well as the aesthetic
properties and strength of the resulting products. In one
embodiment, the at least one filler has an average particle size
less than or equal to about 5 microns. In another embodiment, the
at least one filler has an average particle size ranging from about
1 to about 5 microns. In a further embodiment, the at least one
filler has an average particle size of about 1.5 microns. In yet
another embodiment, the at least one filler has an average particle
size less than or equal to about 4 microns. In yet a further
embodiment, the at least one filler has an average particle size
less than or equal to about 3 microns. In still another embodiment,
the at least one filler has an average particle size less than or
equal to about 2 microns. In still a further embodiment, the at
least one filler has an average particle size less than or equal to
about 1.5 microns. In another embodiment, the at least one filler
has an average particle size less than or equal to about 1 micron.
In a further embodiment, the at least one filler has an average
particle size ranging from about 1 micron to about 4 microns. In
yet another embodiment, the at least one filler has an average
particle size ranging from about 1 micron to about 3 microns. In
yet a further embodiment, the at least one filler has an average
particle size ranging from about 1 micron to about 2 microns. In
still another embodiment, the at least one filler has an average
particle size ranging from about 0.5 microns to about 1.5 microns.
Average particle size is defined herein as the d.sub.50 as measured
on a Microtrac 100 particle size analyzer. Products with average
particle sizes outside the embodied ranges may also be incorporated
into certain embodiments.
[0041] In addition, the at least one filler may be characterized by
a "top cut" value. As used herein, the term "top cut" refers to the
particle diameter at which 98% of the particles in the sample of
filler have a smaller diameter as identified by a Microtrac 100
particle size analyzer. In one embodiment, the at least one filler
has a top cut of about 15 microns or less. In another embodiment,
the top cut is about 10 microns or less. In a further embodiment,
the top cut is about 8 microns or less. In yet another embodiment,
the top cut is about 6 microns or less. In yet a further
embodiment, the top cut is about 4 microns or less. In still
another embodiment, the top cut ranges from about 4 microns to
about 15 microns. In still a further embodiment, the top cut ranges
from about 4 microns to about 12 microns. In another embodiment,
the top cut ranges from about 4 microns to about 10 microns. In a
further embodiment, the top cut ranges from about 4 microns to
about 8 microns. In yet another embodiment, the top cut ranges from
about 4 microns to about 6 microns. In yet a further embodiment,
the at least one filler has a top cut of not more than about 90% of
the average diameter of the spunlaid fiber. In another embodiment,
the at least one filler has a top cut of not more than about 95% of
the average diameter of the spunlaid fiber. In a further
embodiment, the at least one filler has a top cut of not more than
about 100% of the average diameter of the spunlaid fiber.
[0042] The particle size distribution of the at least one filler
according to the present disclosure may be small enough so as to
not significantly weaken the individual fibers and/or make the
surface of the fibers abrasive, but large enough so as to create an
aesthetically pleasing surface texture. For example, processing
problems described as "fiber clumps" may result when fibers break
in the drawing section of the line, e.g., the area in which the
fibers are elongated from the 600 mm size exiting the spinneret
hole of an extrusion apparatus down to an average 16 micron final
fiber diameter. An example of a broken fiber caused by the addition
of too large of calcium carbonate particles is illustrated in FIG.
1. When a fiber breaks it may collide with other fibers, creating a
"bundle" or "clump." One example of a fiber clump is shown in FIG.
2.
[0043] FIG. 3 illustrates a exemplary particle size distribution
(FiberLink.TM. 101S manufactured in the United States by Imerys,
Inc.), wherein less than 5% of the total particles are greater than
5 microns or less than 0.5 microns. Particles above 5 microns may
tend to weaken the structure, and particles less than 0.5 microns
may tend to form agglomerates that lead to formation of structures
greater than 5 microns. However, it has been shown that fillers
such as coated calcium carbonate having a top cut of less than the
diameter of the fibers may be effectively incorporated into the
fibers.
[0044] The at least one filler may be coated with at least one
organic material. In one embodiment, the at least one organic
material is chosen from fatty acids, including but not limited to
stearic acid, and salts and esters thereof, such as stearate. In
another embodiment, the at least one organic material is ammonium
stearate. In a further embodiment, the at least one organic
material is calcium stearate. In yet another embodiment, the at
least one organic material is stearic acid. In yet a further
embodiment, the at least one organic material is salts and esters
of fatty acids. The product FiberLink.TM. 101S sold by Imerys, Inc.
is a non-limiting example of a calcium carbonate product coated
with stearic acid.
[0045] Surface coating the at least one filler with at least one
organic material may serve to improve dispersion of the filler
particles throughout the fiber and facilitate the overall
production of the fibers. For example, the addition of uncoated
calcium carbonate to at least one polymeric resin (as shown in FIG.
4), as opposed to coated calcium carbonate (as shown in FIG. 7),
results in fibers having uncoated calcium carbonate particles
located on the outside of the fibers, which is problematic because
uncoated particles located on the outside of the fibers may cause
the fibers to attach to metal components of the spinneret die holes
and clog the exit holes, thus preventing the fibers from extruding
properly if at all.
[0046] The amount of the at least one filler may negatively impact
the strength and/or surface texture of the fibers once it exceeds a
certain value. Thus, excessive amounts of the at least one filler
should generally not be incorporated in the fibers. In one
embodiment, the at least one filler is present in an amount less
than about 40 wt % relative to the total weight of the fibers. In
another embodiment, the at least one filler is present in an amount
less than about 25 wt %. In a further embodiment, the at least one
filler is present in an amount less than about 15 wt %. In yet
another embodiment, the at least one filler is present in an amount
less than about 10 wt %. In yet a further embodiment, the at least
one filler is present in an amount ranging from about 5 wt % to
about 40 wt %. In still another embodiment, the at least one filler
is present in an amount ranging from about 10 wt % to about 25 wt
%. In still another embodiment, the at least one filler is present
in an amount ranging from about 10 wt % to about 15 wt %. In yet
another embodiment, the at least one filler is present in an amount
from about 5 wt % to about 40 wt % when the at least one filler has
an average particle size of less than about 3 microns and/or a top
cut of about 8 microns or less. In yet a further embodiment, the at
least one filler is present in an amount from about 5 wt % to about
40 wt % when the at least one filler is coated and has an average
particle size of less than about 100% of the average diameter of
the spunlaid fibers. In another embodiment, the at least one filler
is present in an amount less than about 35 wt %.
[0047] Optional Additives
[0048] In addition to the at least one polymeric resin and the at
least one filler, the spunlaid fibers may further comprise at least
one additive. The at least one additive may be chosen from those
now known in the art or those hereafter discovered. In one
embodiment, the at least one additive is chosen from additional
mineral fillers, including but not limited to talc, gypsum,
diatomaceous earth, kaolin, attapulgite, bentonite,
montmorillonite, and other natural or synthetic clays. In another
embodiment, the at least one additive is chosen from inorganic
compounds, including but not limited to silica, alumina, magnesium
oxide, zinc oxide, calcium oxide, and barium sulfate. In a further
embodiment, the at least one additive is chosen from one of the
group consisting of: optical brighteners; heat stabilizers;
antioxidants; antistatic agents; anti-blocking agents; dyestuffs;
pigments, including but not limited to titanium dioxide; luster
improving agents; surfactants; natural oils; and synthetic
oils.
[0049] Fiber Properties
[0050] The exemplary fibers disclosed in Examples 1-12 herein were
produced with the same process parameters and, therefore, have
similar fiber diameters as shown in FIG. 5. The results shown in
FIG. 5 illustrate those fibers are a typical size for commercial
spunbond operations and the sizes do not vary significantly as a
function of coated calcium carbonate content. FIGS. 6 and 7 are SEM
photographs showing the fibers without coated calcium carbonate and
after coated calcium carbonate has been added. It may be difficult
to measure individual fiber properties in a spunlaid web, as the
fibers are entangled during normal production. The process of
separating an individual fiber for testing may damage the fiber so
that the physical properties may be radically changed.
Processes for Producing Spunlaid Fibers
[0051] Spunlaid fibers, as discussed herein, may be produced
according to any appropriate process or processes now known to the
skilled artisan or hereafter discovered that results in the
production of a nonwoven web of fibers comprising at least one
polymeric resin. Two exemplary spunlaid processes are spunbonding
and meltblowing. A spunlaid process may begin with heating the at
least one polymeric resin at least to its softening point, or to
any temperature suitable for the extrusion of the polymeric resin.
In one embodiment, the at least one polymeric resin is heated to a
temperature ranging from about 180.degree. C. to about 240.degree.
C. In another embodiment, the at least one polymeric resin is
heated to from about 200.degree. C. to about 220.degree. C.
[0052] Spunbonded fibers may be produced by any of various
techniques now known or hereafter discovered in the art, including
but not limited to general spun-bonding, flash-spinning,
needle-punching, and water-punching processes. Exemplary
spun-bonding processes are described in Spunbond Technology Today
2--Onstream in the 90's (Miller Freeman (1992)), U.S. Pat. No.
3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matuski
et al., and U.S. Pat. No. 4,340,563 to Appel et al., each of which
is incorporated herein by reference herein in its entirety.
[0053] Meltblown fibers may be produced by any of various
techniques now known or hereafter discovered in the art. For
example, meltblown fibers may be produced by extruding the at least
one polymeric resin and attenuating the streams of resin by hot air
to form fibers with a fine diameter and collecting the fibers to
form spunlaid webs. One example of a meltblown process is generally
described in U.S. Pat. No. 3,849,241 to Buntin, which is
incorporated by reference herein in its entirety.
[0054] The at least one filler may be incorporated into the at
least one polymeric resin using any method conventionally known in
the art or hereafter discovered. For example, the at least one
filler may be added to the at least one polymeric resin during any
step prior to extrusion, for example, during or prior to the
heating step. In another embodiment, a "masterbatch" of at least
one polymeric resin and the at least one filler may be premixed,
optionally formed into granulates or pellets, and mixed with at
least one additional virgin polymeric resin before extrusion of the
fibers. The at least one additional virgin polymeric resin may be
the same or different from the at least one polymeric resin used to
make the masterbatch. In certain embodiments, the masterbatch
comprises a higher concentration of the at least one filler, for
instance, a concentration ranging from about 20 to about 75 wt %,
than is desired in the final product, and may be mixed with the at
least one additional polymeric resin in an amount suitable to
obtain the desired concentration of at least one filler in the
final spunlaid fiber product. For example, a masterbatch comprising
about 50 wt % coated calcium carbonate may be mixed with an equal
amount of at least one virgin polymeric resin to produce a final
product comprising about 25 wt % coated calcium carbonate. The
masterbatch may be mixed and pelletized using any apparatus known
in the art or hereafter discovered, for example, a ZSK 30 Twin
Extruder may be used to mix and extrude the coated calcium
carbonate and at least one polymer resin masterbatch, and a
Cumberland pelletizer may be used to optionally form the
masterbatch into pellets.
[0055] Once the at least one filler or masterbatch is mixed with
the at least one polymeric resin, the mixture may be extruded
continuously through at least one spinneret to produce long
filaments. The extrusion rate may vary according to the desired
application. In one embodiment, the extrusion rate ranges from
about 0.4 g/min to about 2.5 g/min. In another embodiment, the
extrusion rate ranges from about 0.8 to about 1.2 g/min.
[0056] The extrusion temperature may also vary depending on the
desired application. In one embodiment, the extrusion temperature
ranges from about 180 to about 235.degree. C. In another
embodiment, the extrusion temperature ranges from about 200 to
about 215.degree. C. The extrusion apparatus may be chosen from
those conventionally used in the art, for example, the Reicofil 2
apparatus produced by Reifenhauser. The spinneret of the Reicofil
2, for example, contains 4036 holes, approximately 0.6 millimeters
in diameter, in a pattern with approximately 19 alternating rows
across the die.
[0057] After extrusion, the filaments may be attenuated. Spunbonded
fibers, for example, may be attenuated by high-speed drafting, in
which the filament is drawn out and cooled using a high velocity
gas stream, such as air. The gas stream may create a draw force on
the fibers that draws them down into a vertical fall zone to the
desired level. Meltblown fibers may, for example, be attenuated by
convergent streams of hot air to form fibers of fine diameter.
[0058] After attenuation, the fibers may be directed onto a
foraminous surface, such as a moving screen or wire. The fibers may
then be randomly deposited on the surface with some fibers laying
in a cross direction, so as to form a loosely bonded web or sheet.
In certain embodiments, the web is held onto the foraminous surface
by means of a vacuum force. At this point, the web may be
characterized by its basis weight, which is the weight of a
particular area of the web, expressed in grams per square meter
(gsm). In one embodiment, the basis weight of the web ranges from
about 10 to about 55 gsm. In another embodiment, the basis weight
of the web ranges from about 15 to about 30 gsm.
[0059] Once a web is formed, it may be bonded according to any
method conventionally used in the art or hereafter discovered, for
example, melting and/or entanglement methods, such as thermal point
bonding, ultrasonic bonding, hydroentanglement, and through-air
bonding. Thermal point bonding is a commonly used method and
generally involves passing the web of fibers through at least one
heated calender roll to form a sheet. In certain embodiments,
thermal point bonding may involve two calendar rolls where one roll
is embossed and the other smooth. The resulting web may have
thermally embossed points corresponding to the embossed points on
the roll. For example, the web shown in FIG. 8 has diamond shapes
measuring approximately 0.5 mm on each side embossed in a
12.times.12 pattern per square inch.
[0060] After bonding, the resulting sheet may optionally undergo
various post-treatment processes, such as direction orientation,
creping, hydroentanglement, and/or embossing processes. The
optionally post-treated sheet may then be used to manufacture
various nonwoven products. Methods for manufacturing nonwoven
products are generally described in the art, for example, in The
Nonwovens Handbook, The Association of the Nonwoven Industry (1988)
and the Encyclopaedia of Polymer Science and Engineering, vol 10,
John Wiley and Sons (1987).
[0061] Spunlaid fibers may have an average diameter ranging from
about 0.5 microns to about 35 microns or more. In one embodiment,
spunbonded fibers have a diameter ranging from about 5 microns to
about 35 microns. In another embodiment, spunbonded fibers have a
diameter of about 15 microns. In yet another embodiment, spunbonded
fibers have a diameter of about 16 microns. In one embodiment,
meltblown fibers have a diameter ranging from about 0.5 microns to
about 30 microns. In another embodiment, meltblown fibers have a
diameter of about 2 microns to about 7 microns. In a further
embodiment, meltblown fibers have a smaller diameter than
spunbonded fibers of the same or a similar composition. In one
embodiment, the spunbonded or meltblown fibers range in size from
about 0.1 denier to about 120 denier. In another embodiment, the
fibers range in size from about 1 denier to about 100 denier. In a
further embodiment, the fibers range in size from about 1 to about
5 denier. In yet another embodiment, the fibers are about 100
denier in size.
[0062] Spunlaid fibers according to the present invention may have
an increased density over spunlaid fibers made without at least one
coated filler. The increase in density may vary depending on the
amount of the at least one coated filler used in the spunlaid
fibers of the present invention. In one embodiment, the increase is
from about 5% to about 40%. In another embodiment, the increase is
from about 10% to about 30%. In a further embodiment, the increase
is about 30%. For example, spunlaid fibers from pure polypropylene
may have a density of about 0.9 g/cc and float in water, while
spunlaid fibers with about 20% of at least one coated filler chosen
from coated calcium carbonate may have a density of about 1.25 g/cc
and not float in water. The increase in density of the spunlaid
fibers may be useful in several applications, including in products
such as ground cover that are not intended to readily float.
[0063] Some thermoformed spunlaid fibers (e.g., extrusion spun or
melt spun thermoplastic fibers) according to the present invention
may have a different charge density (electrostatic effect) than
thermoformed spunlaid fibers made without at least one coated
filler. The difference in charge density may vary depending on the
amount of the at least one coated filler used in the spunlaid
fibers of the present invention. The difference in electrostatic
effect may be observed, for example, by rubbing the web on human
hair or by simply picking up the webs. The difference in charge
density may be revealed in an increase in positive voltage, a
decrease in negative voltage, a decrease from a positive charge
voltage to a negative charged voltage, or an increase from a
negative charged voltage to a positive charge voltage. In one
embodiment, the difference is from about 10 to about 100 volts. In
another embodiment, the difference is about 90 volts. In a further
embodiment, the difference is about 45 volts. In yet another
embodiment, the difference is from a positive charge density on
spunlaid fibers not made according to the present invention, to a
negative charge density on spunlaid fibers made according to the
present invention. In one embodiment, the charge density of
spunlaid fibers according to the present invention is from about
-10 to about -100 volts. In another embodiment, the charge density
is from about -20 to about -70 volts. In a further embodiment the
charge density is about -25 volts. In yet another embodiment, the
charge density is about -60 volts. The difference in charged
density of the thermoformed spunlaid fibers, or the overall charged
density of the spunlaid fibers, according to the present invention
may be useful in several applications, including in produced such
as filtration media or dust mops.
Testing
[0064] The fibers disclosed herein may be tested by any number of
various methods and for any number of various properties. In one
embodiment, the tests described in ASTM D3822 may be used.
[0065] Dart Drop Test
[0066] The Dart Drop test is carried out by dropping darts onto the
nonwoven sheet from a standard height. The drop is repeated with
darts having steadily increasing weights attached to them. The end
point of the testing is defined as the weight at which half of the
darts form holes where the dart impacted the fabric. This protocol
is described more thoroughly, for example, in ASTM 1709.
[0067] Tensile Strength Test
[0068] Spunlaid fibers are randomly distributed from an extrusion
apparatus onto a moving web to produce nonwoven fabrics. However,
more fibers align in the direction the web is moving, or in the
machine direction (MD), than align in a direction perpendicular to
the machine, called the cross machine direction (CD) or transverse
direction (TD). This may cause the nonwoven fabrics to be stronger
in the machine direction than in the cross machine or transverse
direction.
[0069] The tensile strength test is carried out by cutting one-inch
wide strips of the nonwoven fabric and stretching the fabric
separately along its machine direction and along its cross machine
direction until it breaks. The fabric may be stretched using
standard equipment, such as that sold by Instron. The amount of
force necessary to fracture the fabric is referred to as the
maximum load. The Instron data also indicates the elongation where
the nonwoven fabric breaks. This is referred to as the elongation
to break or maximum percent strain. These tests are conventionally
conducted in both the machine direction and cross machine
direction. Fabrics with tensile strength ratios (MD:CD) of about 1,
also called "square" fabrics, may be preferred in the art.
[0070] Density
[0071] An estimated relative density of two spunlaid webs may be
calculated by measuring the thickness of an embossing point on each
of the two spunlaid webs and taking their ratio.
[0072] Charge Density
[0073] Charge density of spunlaid webs may be measured by charging
a web with a corona charging system (such as the TANTRET Tech-1)
and then testing for surface charge using an appropriate voltmeter
and probe (such as a Monroe Model 244 Isoprobe Electrostatic
Voltmeter with a 1017E Probe). The measurement system may be
interfaced with an appropriate data gathering computer (such as an
IBM AT computer using DT 2801 I/O system (Data Translation Inc.,
Marlborough, Mass.)). One technique for measuring charged density
is described in Tsai et al., "Different Electrostatic Methods for
Making Electret Filters," 54 J. Electrostatics 333-341 (2002),
which is incorporated herein by reference in its entirety.
[0074] Other than in the examples, or where otherwise indicated,
all numbers expressing quantities of ingredients, reaction
conditions, and so forth used in the specification and claims are
to be understood as being modified in all instances by the term
"about." Accordingly, unless indicated to the contrary, the
numerical parameters set forth in the specification and attached
claims are approximations that may vary depending upon the desired
properties sought to be obtained by the present disclosure. At the
very least, and not as an attempt to limit the application of the
doctrine of equivalents to the scope of the claims, each numerical
parameter should be construed in light of the number of significant
digits and ordinary rounding approaches.
[0075] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the invention are approximations,
unless otherwise indicated the numerical values set forth in the
specific examples are reported as precisely as possible. Any
numerical value, however, inherently contain certain errors
resulting from the standard deviation found in their respective
testing measurements.
[0076] The headers used in this specification are presented for the
convenience of the reader and not intended to be limiting of the
inventions described herein. By way of non-limiting illustration,
examples of certain embodiments of the present disclosure are given
below.
EXAMPLES
Examples 1-6
[0077] A masterbatch comprising 50 wt % coated calcium carbonate
(FiberLink.TM. 101S manufactured in the United States by Imerys,
Inc.) and 50 wt % polypropylene homopolymer (Exxon 3155) was
prepared using a ZSK 30 Twin Screw Extruder and pelletized in a
Cumberland pelletizer. FiberLink.TM. 101S has an average particle
size of 1.5 microns and a top cut around 8 microns. The resulting
product was then combined with virgin Exxon 3155 polymer in a
Reicofil 2 extruder to produce fibers. The fibers were collected as
a spunbonded web and subsequently point bonded to produce nonwoven
fabrics comprising from 0 to 25 wt % coated calcium carbonate.
Fabrics comprising 0 and 5 wt % calcium carbonate were included as
comparative examples. The resulting fabrics all exhibited a basis
weight of 25 gsm, except for the fabric comprising 25 wt % coated
calcium carbonate, which had a basis weight of 29 gsm.
[0078] Fiber clumps were observed in nonwoven fabrics comprising
25% FiberLink.TM. 101S. However, it is possible that processing
problems such as this observed at high concentrations of coated
calcium carbonate could have been corrected, for example, by
decreasing the average particle size and/or the top cut of the
calcium carbonate filler.
[0079] Each fabric was subjected to dart drop and tensile strength
tests, the results of which are illustrated in FIGS. 9-13.
[0080] As shown in FIG. 9, the dart drop test results indicate that
the impact properties of the nonwoven fabric are actually improved
by the addition of coated calcium carbonate, most notably in the
range of 10 to 25 wt % coated calcium carbonate.
[0081] As indicated by FIGS. 10 and 11, the tensile properties
(maximum load) in both the machine and transverse directions do not
appear to be substantially adversely affected by the addition of
coated calcium carbonate.
[0082] Finally, FIGS. 12 and 13 illustrate that the elongation
properties (maximum percent strain) in both the machine and
transverse directions are improved with the addition of coated
calcium carbonate, again, most notably in the range of 10 to 25 wt
% coated calcium carbonate.
Examples 7-10
[0083] Using the same machinery and procedure as described above in
Examples 1-6, nonwoven fabrics comprising 0 wt %, 5 wt %, or 20 wt
% coated with one of two calcium carbonates (FiberLink 101S.TM.
manufactured in the United States by Imerys, Inc. and FiberLink.TM.
103S from Imerys, Inc.) were produced. FiberLink.TM. 103S has an
average particle size of about 3 microns and has a top cut of about
15 microns. The moving belt was run progressively faster to
compensate for adding calcium carbonate with a density three times
as high as the polypropylene resin. No processing issues were
experienced when processing these fibers.
[0084] As illustrated in FIG. 14, the resulting fibers ranged from
about 15 microns to about 16 microns in diameter, demonstrating
that the calcium carbonate did not alter the size of the fibers.
More particularly, the results of FIG. 14 illustrate those fibers
are a typical size for commercial spunbond operations and the sizes
do not vary significantly as a function of coated calcium carbonate
content. In addition, the basis weight did not vary among Examples
7-10, with the fabrics all exhibiting an average basis weight of
about 26 gsm, as illustrated in FIG. 15.
[0085] Each fabric was subjected to dart drop and tensile strength
tests, the results of which are illustrated in FIGS. 16-20.
[0086] As shown in FIG. 16, the dart drop test results indicate
that the impact properties of the nonwoven fabric are improved by
the addition of coated calcium carbonate, for example in amounts of
5% and 20%.
[0087] As indicated by FIGS. 17 and 18, the tensile properties
(maximum load) in both the machine and cross directions appear to
be improved in some examples with the addition of coated calcium
carbonate and in other examples do not appear to be substantially
adversely affected by the addition of calcium carbonate.
[0088] Finally, FIGS. 19 and 20 illustrate that the elongation
properties (maximum percent strain) in both the machine and cross
directions are improved with the addition of coated calcium
carbonate, again, for example in amounts of 5% and 20%.
Examples 11-12
[0089] Under the same procedures as described in Examples 1-6, for
Example 11 polypropylene resin was combined with 0%, 5%, or 20%
KOTOMITE.RTM. (a coated calcium carbonate manufactured by Imerys,
Inc.). Standard KOTOMITE.RTM. has an average particle size of about
3 microns and a top cut of about 20 microns, which is higher than
that of FiberLink.TM. 103S. The small size difference between
KOTOMITE.RTM. and FiberLink.TM. 103S is important because the
fibers produced average about 16 microns in diameter. At the higher
concentration, the 20 micron particles caused the fibers to
fracture during the drawing process.
[0090] The 5% KOTOMITE.RTM. experiment ran without obvious defects.
With the addition of 20% KOTOMITE.RTM., the fibers fell vertically
from the die to a point about 24 inches below the spinneret where
some of the fibers broke as shown in FIG. 1. Because of the random
air flow, once a fiber broke, it immediately collided with other
fibers, creating a "bundle." An example of a fiber bundle is
illustrated in FIG. 2. This flaw is considered a defect in the
textile industry and, therefore, KOTOMITE.RTM. may be an unlikely
additive at higher concentrations.
[0091] In addition, ATOMITE.RTM., a type of uncoated calcium
carbonate manufactured by Imerys, Inc., which has a top cut of
about 15 microns, was mixed with polypropylene resin at
concentrations of 0 wt %, 5 wt %, or 20 wt % for Example 12.
However, few fibers were produced from either 5 wt % or 20 wt %
ATOMITE.RTM. because the mixtures immediately began clogging the
spinneret openings. As shown in FIG. 4, it was observed from the
few fibers produced that the uncoated calcium carbonate particles
resided on the outside of the fibers. ATOMITE.RTM. may be an
unlikely additive at these concentrations primarily because the
calcium carbonate it is uncoated. In contrast, examples 7-10 show
that production of fibers comprising coated calcium carbonate, also
having a top cut of about 15 microns, did not result in clogging.
Since Atomite and FiberLink.TM. 103S have similar top cut values
(about 15 microns), it can be seen that whether the calcium
carbonate is coated may also play a role in a successful fiber
production.
Example 13
[0092] Webs comprising 0%, 5%, and 20% coated calcium carbonate
(FiberLink.TM. 101S manufactured in the United Stated by Imerys,
Inc.) were first charged with a corona charging system (TANTRET
Tech-1) and then tested for surface charge using an A Monroe Model
244 Isoprobe Electrostatic Voltmeter with a 1017E Probe. The
measurement system was interfaced with an IBM AT computer using DT
2801 I/O system (Data Translation Inc., Marlborough, Mass.). The
technique was followed as described in Tsai et al., "Different
Electrostatic Methods for Making Electret Filters," 54 J.
Electrostatics 333-341 (2002).
[0093] FIG. 21 shows the difference in potential after
electrostatic charging webs not comprising coated calcium carbonate
(i.e., not in accordance with the present invention) and webs
comprising 5% and 20% coated calcium carbonate in accordance with
the present invention.
* * * * *